Degreeing a Cam, or not.....

[George Jets]

Kent,
Post #113. The procedure I posted was for a single pattern cam. For some reason I thought you were using a SP cam. But it is a dual pattern, so it won't work. Sorry for the confusion.

Thanks for clarifying that.

Just for others looking in:

1967 383 with the small exhaust valve 516 closed chamber heads, had a dual pattern cam.

Ma Mopar designed it that way to hold the small exhaust valve open longer than the larger intake valve so it could better breath out the volume of exhaust gases that were cycling through.

So this puts the lobe centers for intake and exhaust valves at different, not equal degrees.

If my calculations are correct this would put the straight edge test on the pushrods tips on overlap at TDC (or at the recommended degrees of cam advance) leaning to the exhaust valve side, as it is staying open for a longer period of time. The lobe center degrees would not be matching, hence the angle of the straight edge.

Thanks all, find all of this very interesting. It's the whole personality of the engine when it is dialed in right.

Camshaft Lobe Separation

Definition & Description
The Lobe Separation Angle (LSA) is the distance between the centerlines of the intake and exhaust lobes on the camshaft. It is measured in degrees of camshaft rotation.

Intake Centerline + Exhaust Centerline ÷ 2

For example, if the intake is 107° and the exhaust is 117°:

107° + 117° = 224°
224° ÷ 2 = 112° (LSA)

 

[crackedback]

I don't recall if you just did dot to dot. If the numbers you posted are correct 116ish ICL on intake, another in a long line of examples to NEVER trust any markings on a cam/timing set when being installed. Always verify.

It needs to be corrected without question based on your findings.

 

[Kent mosby]

I don't recall if you just did dot to dot. If the numbers you posted are correct 116ish ICL on intake, another in a long line of examples to NEVER trust any markings on a cam/timing set when being installed. Always verify.

It needs to be corrected without question based on your findings.

Yes, My next step is to remove the rockers and test again on the lifters directly. If the results are the same I will break it down completely. Then the only debate is do I replace the camshaft or make the current one work. The reason I contemplate changing it is 2 fold. First, I have changed my thoughts on the use of the car. I no longer want to use nitrous or other boosters so the original cam may not be the best. Second, Many knowledgeable people here say that the cam is not right for the motor. My main purpose now is different from before as well. I no longer want to have just a strip car. Now I have a great street hot rod that I can drive to the track and lay down some good times. I want to be in the lower half of 11s but I don't need to be under 10.90 as I don't want to install a roll cage. This is my current setup and I want to keep the solid lifters if possible.

1973 Plymouth Scamp
RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.5RR, Trick flow single plane intake. Holley super sniper EFI, hyperspark ignition, coil and distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with transgo tf2 valve body mods. B&M Quicksilver shifter. Gear vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs. Competition engineering race shocks. Pypes exhaust 3" into 2.5 inch. RacePro mufflers. Mickey Thompson ET street SS Drag radials 255/60-15 27.3 inch) but going to 275/60-15 28.2 inch diameter. Current cam specs 244/252 @ .050”, 282/290 adv, .516”/.537” lift(1.5:1 rocker), 112 sep, .016”/.018” lash, Solid lifter from Oregon Cams.

FWIW, I have never built a hotrod before. I rebuilt a 1950 chevy 235 motor. When I was young I was a precision machinist for 12 years before, during and after dental school. So I know my way around tools. This car went from and an empty shell without a motor installed and no transmission. I started with a bare block and put everything together, motor, rebuilt the transmission, redid the upholstery.... everything except the body started from scratch. The only time I did not measure and double check the assembly was this dumb omission on the cam degreeing . Oh what I have learned. As Reagan said, "Trust, but Verify". I trusted but did not verify. I enjoy the journey and, while this is a nuisance, I chalk it up to a learning experience. I am better because of it. Many people have very nice that others have built for them and I could have had someone build me a car. That was not what I wanted. I wanted to do it myself. I have. And I thank all of you who have helped me along the way. No way I could have done this without the support and encouragement from FABO. Thanks again for everything.

 

[68383GTS]

That cam is pretty small for a 512.

 

[RustyRatRod]

Yes, My next step is to remove the rockers and test again on the lifters directly. If the results are the same I will break it down completely. Then the only debate is do I replace the camshaft or make the current one work. The reason I contemplate changing it is 2 fold. First, I have changed my thoughts on the use of the car. I no longer want to use nitrous or other boosters so the original cam may not be the best. Second, Many knowledgeable people here say that the cam is not right for the motor. My main purpose now is different from before as well. I no longer want to have just a strip car. Now I have a great street hot rod that I can drive to the track and lay down some good times. I want to be in the lower half of 11s but I don't need to be under 10.90 as I don't want to install a roll cage. This is my current setup and I want to keep the solid lifters if possible.

1973 Plymouth Scamp
RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.5RR, Trick flow single plane intake. Holley super sniper EFI, hyperspark ignition, coil and distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with transgo tf2 valve body mods. B&M Quicksilver shifter. Gear vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs. Competition engineering race shocks. Pypes exhaust 3" into 2.5 inch. RacePro mufflers. Mickey Thompson ET street SS Drag radials 255/60-15 27.3 inch) but going to 275/60-15 28.2 inch diameter. Current cam specs 244/252 @ .050”, 282/290 adv, .516”/.537” lift(1.5:1 rocker), 112 sep, .016”/.018” lash, Solid lifter from Oregon Cams.

FWIW, I have never built a hotrod before. I rebuilt a 1950 chevy 235 motor. When I was young I was a precision machinist for 12 years before, during and after dental school. So I know my way around tools. This car went from and an empty shell without a motor installed and no transmission. I started with a bare block and put everything together, motor, rebuilt the transmission, redid the upholstery.... everything except the body started from scratch. The only time I did not measure and double check the assembly was this dumb omission on the cam degreeing . Oh what I have learned. As Reagan said, "Trust, but Verify". I trusted but did not verify. I enjoy the journey and, while this is a nuisance, I chalk it up to a learning experience. I am better because of it. Many people have very nice that others have built for them and I could have had someone build me a car. That was not what I wanted. I wanted to do it myself. I have. And I thank all of you who have helped me along the way. No way I could have done this without the support and encouragement from FABO. Thanks again for everything.

Check out grind #1281. I don't know what sprAngs you have, so you may need to change them to accommodate that camshaft.....maybe not.

http://www.oregoncamshaft.com/Mechanical-Cam-Specs.html

 

[512Stroker]

Yes, My next step is to remove the rockers and test again on the lifters directly. If the results are the same I will break it down completely. Then the only debate is do I replace the camshaft or make the current one work. The reason I contemplate changing it is 2 fold. First, I have changed my thoughts on the use of the car. I no longer want to use nitrous or other boosters so the original cam may not be the best. Second, Many knowledgeable people here say that the cam is not right for the motor. My main purpose now is different from before as well. I no longer want to have just a strip car. Now I have a great street hot rod that I can drive to the track and lay down some good times. I want to be in the lower half of 11s but I don't need to be under 10.90 as I don't want to install a roll cage. This is my current setup and I want to keep the solid lifters if possible.

1973 Plymouth Scamp
RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.5RR, Trick flow single plane intake. Holley super sniper EFI, hyperspark ignition, coil and distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with transgo tf2 valve body mods. B&M Quicksilver shifter. Gear vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs. Competition engineering race shocks. Pypes exhaust 3" into 2.5 inch. RacePro mufflers. Mickey Thompson ET street SS Drag radials 255/60-15 27.3 inch) but going to 275/60-15 28.2 inch diameter. Current cam specs 244/252 @ .050”, 282/290 adv, .516”/.537” lift(1.5:1 rocker), 112 sep, .016”/.018” lash, Solid lifter from Oregon Cams.

FWIW, I have never built a hotrod before. I rebuilt a 1950 chevy 235 motor. When I was young I was a precision machinist for 12 years before, during and after dental school. So I know my way around tools. This car went from and an empty shell without a motor installed and no transmission. I started with a bare block and put everything together, motor, rebuilt the transmission, redid the upholstery.... everything except the body started from scratch. The only time I did not measure and double check the assembly was this dumb omission on the cam degreeing . Oh what I have learned. As Reagan said, "Trust, but Verify". I trusted but did not verify. I enjoy the journey and, while this is a nuisance, I chalk it up to a learning experience. I am better because of it. Many people have very nice that others have built for them and I could have had someone build me a car. That was not what I wanted. I wanted to do it myself. I have. And I thank all of you who have helped me along the way. No way I could have done this without the support and encouragement from FABO. Thanks again for everything.

You have a long way to go to get into the eleven's.
It's not all cubic inches to take a car into the elevens.
Good luck with that.

 

[Kent mosby]

You have a long way to go to get into the eleven's.
It's not all cubic inches to take a car into the elevens.
Good luck with that.

I understand that it is not all cubic inches. But at 12.3 I don’t think I am that far off. The car works pretty well. I am not at the limit with traction. It does not slip at the line so I am not overpowering the car right now. Plus, I only have 15 or so trips. I am the weakest link. I am ready to do what is needed to make it work but I may also change my goals. As it is, I want to get the most out of what I have. The current situation is not doing so.

 

[cookietruck]

i think the cam is enough to get in the 11's since you have such good heads. I would fix the ICL on the cam and run it for a bit. I would be real curious to see how much better it runs and how much more cranking psi you get just from getting the cam in 4* advanced instead of 4* retarded.
I think i'd look at a better converter before I went to a rowdier cam..

 

[Bewy]

That cam is well down in lift by about 0.035" for the Chrysler 0.904" lifter. Maybe a Chebby grind.

 

[George Jets]

Yes, My next step is to remove the rockers and test again on the lifters directly. If the results are the same I will break it down completely. Then the only debate is do I replace the camshaft or make the current one work. The reason I contemplate changing it is 2 fold. First, I have changed my thoughts on the use of the car. I no longer want to use nitrous or other boosters so the original cam may not be the best. Second, Many knowledgeable people here say that the cam is not right for the motor. My main purpose now is different from before as well. I no longer want to have just a strip car. Now I have a great street hot rod that I can drive to the track and lay down some good times. I want to be in the lower half of 11s but I don't need to be under 10.90 as I don't want to install a roll cage. This is my current setup and I want to keep the solid lifters if possible.

1973 Plymouth Scamp
RB 512ci, 440 source stroker kit with lightweight crankshaft, forged pistons, 10.83 CR. Trick Flow 240 heads, 440 source aluminum rockers 1.5RR, Trick flow single plane intake. Holley super sniper EFI, hyperspark ignition, coil and distributor. TTI 2 inch headers. Hughes 3000 stall converter. 727 transmission with transgo tf2 valve body mods. B&M Quicksilver shifter. Gear vendors overdrive to 8 3/4 rear end with 3.91 gears, braced in back. SS leaf springs. Competition engineering race shocks. Pypes exhaust 3" into 2.5 inch. RacePro mufflers. Mickey Thompson ET street SS Drag radials 255/60-15 27.3 inch) but going to 275/60-15 28.2 inch diameter. Current cam specs 244/252 @ .050”, 282/290 adv, .516”/.537” lift(1.5:1 rocker), 112 sep, .016”/.018” lash, Solid lifter from Oregon Cams.

FWIW, I have never built a hotrod before. I rebuilt a 1950 chevy 235 motor. When I was young I was a precision machinist for 12 years before, during and after dental school. So I know my way around tools. This car went from and an empty shell without a motor installed and no transmission. I started with a bare block and put everything together, motor, rebuilt the transmission, redid the upholstery.... everything except the body started from scratch. The only time I did not measure and double check the assembly was this dumb omission on the cam degreeing . Oh what I have learned. As Reagan said, "Trust, but Verify". I trusted but did not verify. I enjoy the journey and, while this is a nuisance, I chalk it up to a learning experience. I am better because of it. Many people have very nice that others have built for them and I could have had someone build me a car. That was not what I wanted. I wanted to do it myself. I have. And I thank all of you who have helped me along the way. No way I could have done this without the support and encouragement from FABO. Thanks again for everything.

I like your car, I like the way you are doing your car however you want to do it. I like the cam you selected as it may give you better drivability on the street. Now that your goals have changed.

Reading through your list of components, I see you have a gear vender overdrive unit that is great for freeway driving, 75 mph so you are not over revving the engine just going down the highway, with the 3.91 rear gears.

On the flip side the gear vender's extra set of gears, bearings, and fluid could be just enough extra resistance to burn the 1 second time off from your 11 second 1/4 mile goal.

Not easy making it both a drag car and a street car to drive to the track.

Like the whole car and the fact you are doing it yourself.

Following along here.

Thanx

☆☆☆☆☆

 

[PRH]

I don’t know how fussy your track is about enforcing the roll bar rule, but for cars of this vintage, anything quicker than 11.50 is going to require a roll bar to be “legal”.

Everyone loves to blame the cam when the car doesn’t run the number.......... the Comp XS282S, which has specs extremely close to yours has powered many cars(with lesser heads and cubes) well into the 11’s.

The bigger the cam, the less EFI friendly it will be.

Also, the cam and the converter really need to be on the same page if you’re chasing ET’s.........and 3000 stall doesn’t really lend itself as a good match for a “big” cam.

 

[Outsder]

So just out of curiosity, were you able to measure the cranking compression? Would be interested in the numbers as found and after the cam move.

 

[Kent mosby]

So just out of curiosity, were you able to measure the cranking compression? Would be interested in the numbers as found and after the cam move.

I just bought a new tester and tested the driver's side cylinders. All are at 162 psi give or take a pound or so. Later tonight or tomorrow I will test the passenger side and then move the cam and retest. I will post results. What should I see change for the better or worse? Would an increase in cranking compression be optimal?

 

[Kent mosby]

OK.. This may be another stupid question. Or a good idea? . What would be the issue if I simply changed the rockers to 1.6 RR?? According to the cam card I would go to 550 lift intake and 573 exhaust. But what would it do to everything else? timing, performance characteristics, driveability etc.

 

[Outsder]

Thanks for the update, I was curious about cranking compression. One reason I asked is that seems like your 60' time was a little anemic for such a combination.

Yes you would expect the pressure to increase with advancing the cam. How much? I believe I could move and check it, faster and more accurately to determine the change, than I could could calculate it on paper; but that's me.

In general I have found that moving the cam has less effect, then something like milling the heads for a point of compression reduction. I have no experience with running aluminum heads, but I see some posts related to a higher cranking comp tolerance. That said, I have a current iron head 440 that is around 185psi that runs on pump gas with the timing, etc. combination.

Higher ratio rockers can give a nice semi-external tuning option assuming you've got plenty of valve to piston clearance and there is no rocker to retainer clearance issues; diff length pushrods may be required also, but you'll have to trial check. However, being a semi-old index racer type, I would recommend just changing the cam position and run it first and see what happens. One change at time and see what it really does.

 

[PRH]

I’d expect 1.6 rockers to perk it up a bit.

162psi cranking pressure out of a 10.8:1 512 and that cam seems kinda low.
Further evidence that the cam is likely retarded some.

 

[Kent mosby]

Thanks for the update, I was curious about cranking compression. One reason I asked is that seems like your 60' time was a little anemic for such a combination.

Yes you would expect the pressure to increase with advancing the cam. How much? I believe I could move and check it, faster and more accurately to determine the change, than I could could calculate it on paper; but that's me.

In general I have found that moving the cam has less effect, then something like milling the heads for a point of compression reduction. I have no experience with running aluminum heads, but I see some posts related to a higher cranking comp tolerance. That said, I have a current iron head 440 that is around 185psi that runs on pump gas with the timing, etc. combination.

Higher ratio rockers can give a nice semi-external tuning option assuming you've got plenty of valve to piston clearance and there is no rocker to retainer clearance issues; diff length pushrods may be required also, but you'll have to trial check. However, being a semi-old index racer type, I would recommend just changing the cam position and run it first and see what happens. One change at time and see what it really does.

Thanks. The good thing is that changing the rockers will not involve removing anything but the valve covers to access. I will check valve clearance before I do anything else.

 

[Kent mosby]

I am awaiting a crankshaft turning nut, degree wheel, testing springs (so I can check clearance PV). I will then check the whole thing again. Since this picture I have moved the gears to 8*ADV. Hopefully this sets it up correctly. Also, I hope that anyone contemplating just installing dot to dot will think twice about it since they know what I went through.
Does anyone have any thoughts on the idea of just changing rocker ratios to give more lift instead of changing the cam. In Andy Finkbeiner's book he mentions even changing the rocker ratios using a larger 1.6 on the intake side and smaller 1.5 on the exhaust side. If I did that it would be easy to do and I would not have to break in a cam with all that goes with that. That would give me .550 lift on the intake side and .537 on the exhaust. This may change things other than lift such as duration. Any wisdom about that approach??

 

[George Jets]

1.6 rockers will change Lift, but not Duration.

 

[Kent mosby]

1.6 rockers will change Lift, but not Duration.

This was from another site. He said it, and it was on the internet so it must be true........ The author also says that if you change the ratio, then you change the lash as well. But I don't know anything about it.


Post by CamKing » Mon Jun 16, 2008 9:50 am

Here's what happens at the valve when you go from a 1.5 to a 1.6 rocker on my cam that's [email protected]" and .444" lobe lift.

1.5 rocker w/.018" hot lash
316 seat duration
[email protected]"(net valve lift)
[email protected]"
[email protected]"
[email protected]"
[email protected]"
[email protected]"
[email protected]"
[email protected]"
.648" net valve lift

1.6 rocker w/.019" hot lash
316 seat duration
[email protected]" +1
[email protected]" +2
[email protected]" +3
[email protected]" +4
[email protected]" +6
[email protected]" +8
[email protected]" +11
[email protected]" +22
.691" net valve lift +.043"

 

[PRH]

Here's what happens at the valve when you go from a 1.5 to a 1.6 rocker

The duration @“x” lift does change at the valve.

I’d just buy a complete set of 1.6’s...... and then you’ll have a complete set of 1.5’s to sell.

 

[George Jets]

Following along to see what your final goal cam settings are.

Not easy wrapping everyone's head around this way out here in Internet Land.

So you are saying you advanced the cam now 8*, seems like a lot. And if you take into account the ground in advance degrees by the manufacturer.

Could be 10* to 12* cam advance by the time you are done.

From what I am gathering you are shooting for 108* lobe center on the intake and 116* lobe center on the exhaust.

Giving you a LSA Lobe Separation Angle of 112* when you are all finished if you are going to set it up as per mfg recommended specs.

Taking the true test with the degree wheel should tell you where you are at right now with your 8* cam advance setting.

Lots of keyway slots in that crank gear, the more slots the more chances of it not being right. Some people have even set their cam advance to 4* retarded when they really wanted it 4* advanced, not knowing what side of TDC to be working from.

So yeah, check, check, then check again.

__________

As stated by Kent Mosby earlier:

Since this picture I have moved the gears to 8*ADV. Hopefully this sets it up correctly

 

[PRH]

Regardless of where it’s “supposed to be”, the fact is...... you line up the dots, take your reading and it is where it is.
If that isn’t where you want it...... you move it........ however much it takes to put it where you want it.

The motor doesn’t know or care about where the dots on the timing set are.
It only reacts to where the lobes are phased in relationship to the crank(which is often not the same as what the dots would indicate).

If you have a cam with an LSA of 110*, and it’s in the motor with the timing set at “+8*”, but the degree wheel says the cam is in at 112*........ the cam isn’t advanced........ as far as the motor is concerned, it’s retarded 2*.

 

[Kent mosby]

View attachment 1715767094

Regardless of where it’s “supposed to be”, the fact is...... you line up the dots, take your reading and it is where it is.
If that isn’t where you want it...... you move it........ however much it takes to put it where you want it.

The motor doesn’t know or care about where the dots on the timing set are.
It only reacts to where the lobes are phased in relationship to the crank(which is often not the same as what the dots would indicate).

If you have a cam with an LSA of 110*, and it’s in the motor with the timing set at “+8*”, but the degree wheel says the cam is in at 112*........ the cam isn’t advanced........ as far as the motor is concerned, it’s retarded 2*.

The way I am approaching this is that my setup at 0 dot to dot is off by 8 degrees. I will check it at the 8* advanced. If I get the lobes in the correct orientation per the cam card, I am golden. If not I have 9 settings to get it correct. If it happens to be that I am in the middle and must go either 1 degree advanced or retarded from the cam card, what would be the best to do? I will get the parts on Tuesday or Wednesday. I will post findings and seek counsel or advice before closing it up.

 

[George Jets]

View attachment 1715767094

The way I am approaching this is that my setup at 0 dot to dot is off by 8 degrees. I will check it at the 8* advanced. If I get the lobes in the correct orientation per the cam card, I am golden. If not I have 9 settings to get it correct. If it happens to be that I am in the middle and must go either 1 degree advanced or retarded from the cam card, what would be the best to do? I will get the parts on Tuesday or Wednesday. I will post findings and seek counsel or advice before closing it up.

OK that is making sense now. Waiting to see how it checks out with the degree wheel.

PRH can answer your 1* setting questions if it comes to that.

Sake of conversation: If it was 1* additional advanced, that would be
109* intake centerline
117* exhaust centerline
with 113* LSA

If it were 1* less advance, that would be
107* intake centerline
115* exhaust centerline
With 111 LSA (Lobe Separation Angles)

To advance the camshaft in relation to the crankshaft you rotate the cam gear "Clockwise" as you are looking at the front of if the engine.

(moving the cam gear "Counterclockwise" you would be Retarding the camshaft in relation to the crankshaft)

Sound about right @PRH ???